GroStar GS2 Soil pH Pen

Take pH Readings Straight From the Root Zone

A liquid-solution pH pen isn't built to survive being pushed directly into soil, coco, or a rockwool block, and testing runoff instead of the media itself only tells part of the story about what roots are actually experiencing. The GroStar GS2 uses an impact-resistant spear glass tip, rated 10x stronger than a standard probe, so it can be inserted straight into growing media for a direct root-zone pH reading.

Its Swiss LabSen sensor is built for that direct-insertion use case, and the pen ships with calibration solutions, a brush, and a dibber to pre-punch tougher media before inserting the tip.

Key Features & Benefits

• Impact-resistant spear glass tip — rated 10x stronger than a standard probe tip for direct insertion into growing media.
• Swiss LabSen sensor technology — built specifically for accurate, direct readings taken in soil, coco, and rockwool rather than liquid solution alone.
• Reads pH and temperature — gives both root-zone acidity and media temperature from a single insertion.
• Includes a dibber for tougher media — pre-punches dense soil or coco before inserting the probe tip, protecting it from unnecessary strain.
• Ships with calibration solutions, a brush, and IP67 housing — ready to calibrate, clean, and use directly in media out of the box.

Who Should Use the GS2

Growers who want a direct root-zone pH reading from soil, coco, or rockwool — rather than relying only on runoff or reservoir testing — are the fit for the GS2, particularly anyone troubleshooting a media pH that doesn't match what runoff numbers suggest.

About GroStar

The GS2 is part of the GroStar meter line manufactured by Apera Instruments, a water-quality and horticultural testing equipment maker, purpose-built as the soil-insertion model within GroStar's broader pH and EC pen lineup.

Frequently Asked Questions

How is the GS2 different from a standard liquid pH pen?

A standard pH pen is built for liquid solution and isn't designed to survive being pushed into soil or a rockwool block, while the GS2's spear glass tip is rated 10x stronger specifically for that kind of direct insertion. That difference is what makes it a soil-rated pen rather than a reservoir-only one.

When should I use a dibber before inserting the probe?

Use the included dibber to pre-punch a hole in dense or compacted media, like heavier soil blends or a firm coco mix, before inserting the probe tip. That step reduces the strain on the glass tip and helps it seat cleanly for an accurate reading.

Can the GS2 be used in rockwool as well as soil?

Yes, it's rated for direct readings in soil, coco, and rockwool, giving one pen coverage across the common growing media types rather than requiring a separate tool per substrate. Just clean the spear tip between readings when switching between different media types.

How do I clean the probe between readings?

Use the included brush to clear media residue from the tip after each insertion, since built-up soil or coco can affect both the reading and the probe's longevity. Rinse with water if the brush alone doesn't fully clear it.

What's included when I buy the GS2?

It ships with calibration solutions, a cleaning brush, a dibber for tougher media, and an IP67-rated housing, so it's ready to calibrate and use directly in growing media out of the box. Keeping the dibber and brush together with the pen makes routine media checks quicker.